The invention relates to motorcycles, and more particularly to motorcycles having overhead valve or overhead cam engines.
The use of overhead valve and overhead cam engines is well-known in the motorcycle industry. These engines have several distinguishing features, one of which is a valve cover mounted on the cylinder head. The valve cover defines the upper portion of either the rocker box (for overhead valve engines) or the cam case (for overhead cam engines).
The valve cover is typically a one-piece casting that has a lower peripheral edge corresponding in shape to the upper peripheral edge of the cylinder head. The valve cover is mounted on the cylinder head over the valve drive (e.g., rockers and valves or cams and valves). A sealing gasket is commonly used to seal the joint between the cylinder head and the valve cover.
The assembled engine is supported by the frame of the motorcycle. Since access to the valves is needed for valve drive adjustment, maintenance, and repair during the life of the motorcycle, it is desirable to design the frame such that the valve cover can be removed from the cylinder head when the engine is mounted to the frame. The frame must offer enough clearance for the valve cover to be lifted and removed from the cylinder head without catching on the valve drive components. Typically, this requires a significant gap between the valve cover and the frame.
The valve cover of the present invention is designed to minimize the clearance needed to remove the valve cover from the cylinder head. By reducing the necessary clearance between the valve cover and the frame, the size of the gap between the valve cover and the frame can be reduced. This reduction facilitates a more compact motorcycle design.
More specifically, the invention provides a motorcycle engine capable of being supported within a frame. The engine includes a cylinder head having an upper peripheral edge and a valve cover having an assembled width and a lower peripheral edge substantially corresponding in shape to the upper peripheral edge of the cylinder head. The valve cover includes first and second portions coupled together along an engagement surface that does not extend across the entire assembled width of the valve cover. The second portion is separable from the first portion along the engagement surface to facilitate removal of the first portion from the engine. In one aspect of the invention, the first and second portions are separate castings.
The invention also provides a method of assembling a valve cover for a motorcycle engine. The engine is supported in a frame defining a first side and a second side, and the engine includes a cylinder head having an upper peripheral edge spaced from a portion of the frame. The method includes inserting a first portion of a valve cover having an assembled width from the first side, into a space between the upper peripheral edge and the frame, and at a first angular orientation with respect to the frame and the cylinder head, changing the angular orientation of the first portion with respect to the frame and the cylinder head by tilting at least part of the first portion toward the cylinder head, engaging the first portion with the upper peripheral edge of the cylinder head, inserting a second portion of the valve cover from the second side into the space between the upper peripheral edge and the frame, and engaging the second portion of the valve cover with the first portion of the valve cover along an engagement surface that does not extend across the entire assembled width. In one aspect of the invention, the method further includes positioning a sealing gasket between the upper peripheral edge and the first portion.